Piston for compressor

ABSTRACT

A piston for a compressor is disclosed. The piston for the compressor compressing and discharging a refrigerant sucked into a cylinder includes a sliding portion disposed in the cylinder and having a suction space to receive the sucked refrigerant, a head portion coupled to the sliding portion, a compression space being formed at a front of the head portion and the suction space being formed at a rear of the head portion, the head portion comprising a suction port communicating the suction space with the compression space, a press-fit cap coupled to the front of the head portion, the press-fit cap comprising a suction hole connected to the suction port, and a first elastic member disposed between the press-fit cap and the head portion. A gas layer is formed between the head portion, the press-fit cap, and the first elastic member.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korea Patent Application No.10-2020-0003291, filed on Jan. 9, 2020, which is incorporated herein byreference for all purposes as if fully set forth herein.

TECHNICAL FIELD

The present disclosure relates to a piston for a compressor. Morespecifically, the present disclosure relates to a piston for a linearcompressor compressing a refrigerant by a linear reciprocating motion ofthe piston and a linear compressor including the piston.

BACKGROUND

In general, a compressor refers to a device that is configured toreceive power from a power generator such as a motor or a turbine andcompress a working fluid such as air or a refrigerant. Morespecifically, the compressors are widely used in the whole industry orhome appliances, especially a steam compression refrigeration cycle(hereinafter, referred to as “refrigeration cycle”).

The compressors may be classified into a reciprocating compressor, arotary compressor, and a scroll compressor according to a method ofcompressing the refrigerant.

The reciprocating compressor uses a method in which a compression spaceis formed between a piston and a cylinder, and the piston linearlyreciprocates to compress a fluid. The rotary compressor uses a method ofcompressing a fluid by a roller that eccentrically rotates inside acylinder. The scroll compressor uses a method of compressing a fluid byengaging and rotating a pair of spiral scrolls.

Recently, among the reciprocating compressors, the use of linearcompressors that use a linear reciprocating motion without using a crankshaft is gradually increasing. The linear compressor has advantages inthat it has less mechanical loss resulting from switching a rotarymotion to the linear reciprocating motion and thus can improve theefficiency, and has a relatively simple structure.

The linear compressor is configured such that a cylinder is positionedin a casing forming a sealed space to form a compression chamber, and apiston covering the compression chamber reciprocates inside thecylinder. The linear compressor repeats a process in which a fluid inthe sealed space is sucked into the compression chamber while the pistonis positioned at a bottom dead center (BDC), and the fluid of thecompression chamber is compressed and discharged while the piston ispositioned at a top dead center (TDC).

A compression unit and a drive unit are installed inside the linearcompressor. The compression unit performs a process of compressing anddischarging a refrigerant while performing a resonant motion by aresonant spring through a movement generated in the drive unit.

The piston of the linear compressor repeatedly performs a series ofprocesses of sucking the refrigerant into the casing through a suctionpipe while reciprocating at high speed inside the cylinder by theresonant spring, and then discharging the refrigerant from a compressionspace through a forward movement of the piston to move it to a condenserthrough a discharge pipe.

Referring to FIG. 12, Korean Patent No. 10-1990140 discloses that asuction port 1011 introducing a refrigerant into a compression space isformed in a front portion of a piston 1010, and a suction valve 1020that opens and closes the suction port 1011 is provided in front of thesuction port 1011.

The plurality of suction ports 1011 are formed to be spaced apart from acenter C of a coupling hole 1012 in a radial direction by apredetermined length.

The suction valve 1020 is fastened to a piston 10 by a valve couplingmember 1030 and includes a fixing part 1021 to which the valve couplingmember 1030 is coupled, and a plurality of openings 1022 extended in anoutward direction of the fixing part 1021. In this instance, theplurality of openings 1022 may be bent to the front to open the suctionport 1011 and may be returned to the rear to close the suction port1011.

However, a high temperature and high pressure gas compressed in thecompression space acts as a heat source and generates heat transfer to acylinder, the piston 1010, and the sucked refrigerant that have arelatively low temperature, leading to a heat loss and a reduction incompression efficiency.

Prior Art Document

(Patent Document 1) Korean Patent No. 10-1990140 B (published on Jun.18, 2019)

SUMMARY

An object of the present disclosure is to provide a piston for acompressor capable of preventing a heat loss and improving compressionefficiency.

Particular implementations described herein provide a piston for acompressor. The compressor may include a cylinder configured to receivea refrigerant and be configured to compress and discharge therefrigerant in the cylinder. The piston may include a sliding portion, ahead portion, a press-fit cap, and a first elastic member. The slidingportion may be disposed in the cylinder and define a suction space thatreceives the refrigerant. The head portion may be connected to thesliding portion and include a suction port that fluidly communicateswith a compression space and the suction space. The compression spacemay be defined at a first side of the head portion. The suction spacemay be defined at a second side of the head portion opposite to thefirst side of the head portion. The press-fit cap may be connected tothe first side of the head portion. The press-fit cap may include asuction hole that fluidly communicates with the suction port of the headportion. The first elastic member may be disposed between the press-fitcap and the head portion. The head portion, the press-fit cap, and thefirst elastic member may define a gas layer.

In some implementations, the piston described herein may optionallyinclude one or more of the following features. The first elastic membermay have a circular band shape. The first elastic member may be disposedradially closer to an axis of the piston than the suction port of thehead portion. The piston may include a second elastic member disposedbetween the press-fit cap and the head portion around the first elasticmember. The second elastic member may have a circular band shape. Thesecond elastic member may be disposed radially farther from an axis ofthe piston than the suction port of the head portion. A space betweenthe first elastic member and the second elastic member may fluidlycommunicate with the suction port and the suction hole. The head portionmay include a coupling groove that is defined at the first side of thehead portion and spaced apart from the suction port. The piston mayinclude a coupling member that couples the press-fit cap to the firstside of the head portion. The press-fit cap may include a coupling holethat is aligned with the coupling groove of the head portion. Thecoupling member may extend through the coupling hole and is coupled tothe coupling groove. The first elastic member may be disposed betweenthe coupling groove and the suction port. The head portion may include agas groove between the coupling groove and the suction port. The headportion, the press-fit cap, the first elastic member, and the gas groovemay define the gas layer. The gas groove may extend axially at the firstside of the head portion. The gas groove may have a circular band shape.

Particular implementations described herein provide a piston for acompressor. The compressor may include a cylinder configured to receivea refrigerant and be configured to compress and discharge therefrigerant in the cylinder. The piston may include a sliding portion, ahead portion, and a heat insulating member. The sliding portion may bedisposed in the cylinder and define a suction space that receives therefrigerant. The head portion may be connected to the sliding portionand include a suction port that fluidly communicates with a compressionspace and the suction space. The compression space may be defined at afirst side of the head portion. The suction space may be defined at asecond side of the head portion opposite to the first side of the headportion. The heat insulating member may be connected to the first sideof the head portion. The heat insulating member may include a suctionport reception hole that at least partially receives the suction port ofthe head portion.

In some implementations, the piston described herein may optionallyinclude one or more of the following features. The suction port mayprotrude axially from the first side of the head portion. The headportion may include a coupling port that protrudes axially from thefirst side of the head portion and is spaced apart from the suctionport. The piston may include a coupling member that couples the heatinsulating member to the first side of the head portion. The heatinsulating member may include a coupling port reception hole that atleast partially receives the coupling port. The coupling member mayextend through the coupling port reception hole and is coupled to thecoupling port. The piston may include a first elastic member disposedbetween the heat insulating member and the head portion. The headportion, the heat insulating member, and the first elastic member maydefine a gas layer. The first elastic member may have a circular bandshape. The piston may include a second elastic member disposed betweenthe heat insulating member and the head portion around the first elasticmember.

In one aspect, there is provided a piston used in a compressorcompressing and discharging a refrigerant sucked into a cylinder, thepiston comprising a sliding portion disposed in the cylinder and havinga suction space to receive the sucked refrigerant; a head portioncoupled to the sliding portion, a compression space being formed at afront of the head portion and the suction space being formed at a rearof the head portion, the head portion comprising a suction portcommunicating the suction space with the compression space; a press-fitcap coupled to the front of the head portion, the press-fit capcomprising a suction hole connected to the suction port; and a firstelastic member disposed between the press-fit cap and the head portion,wherein a gas layer is formed between the head portion, the press-fitcap, and the first elastic member.

The first elastic member may be formed in a circular band shape.

The first elastic member may be disposed inside the suction port.

The piston for the compressor may further comprise a second elasticmember disposed between the press-fit cap and the head portion andoutside the first elastic member.

The second elastic member may be formed in a circular band shape, andthe second elastic member may be disposed outside the suction port.

A space between the first elastic member and the second elastic membermay communicate with the suction port and the suction hole.

The head portion may comprise a coupling groove formed in a centralregion of a front surface of the head portion, and the suction port maybe spaced apart from the coupling groove.

The piston for the compressor may further comprise a coupling memberconfigured to couple the press-fit cap to the front of the head portion.The press-fit cap may comprise a coupling hole that is formed in acentral region of the press-fit cap and corresponds to the couplinggroove, and the coupling member may pass through the coupling hole andmay be coupled to the coupling groove.

The first elastic member may be disposed between the coupling groove andthe suction port.

The head portion may comprise a gas groove between the coupling grooveand the suction port.

The gas layer may be formed between the head portion, the press-fit cap,the first elastic member, and the gas groove.

The gas groove may extend rearward from the front surface of the headportion.

The gas groove may be formed in a circular band shape.

In another aspect, there is provided a piston used in a compressorcompressing and discharging a refrigerant sucked into a cylinder, thepiston comprising a sliding portion disposed in the cylinder and havinga suction space to receive the sucked refrigerant; a head portioncoupled to the sliding portion, a compression space being formed at afront of the head portion and the suction space being formed at a rearof the head portion, the head portion comprising a suction portcommunicating the suction space with the compression space; and a heatinsulating member coupled to the front of the head portion, the heatinsulating member comprising a suction port hole in which the suctionport is disposed.

The suction port may protrude forward from a front surface of the headportion.

The head portion may comprise a coupling port that protrudes forward ina central region of the front surface of the head portion, and thesuction port may be spaced apart from the coupling port.

The piston for the compressor may further comprise a coupling memberconfigured to couple the heat insulating member to the front of the headportion. The heat insulating member may comprise a coupling port holewhich is formed in a central region of the heat insulating member and inwhich the coupling port is disposed. The coupling member may passthrough the coupling port hole and may be coupled to the coupling port.

The piston for the compressor may further comprise a first elasticmember disposed between the heat insulating member and the head portion.A gas layer may be formed between the head portion, the heat insulatingmember, and the first elastic member.

The first elastic member may be formed in a circular band shape.

The piston for the compressor may further comprise a second elasticmember disposed between the heat insulating member and the head portionand outside the first elastic member.

The present disclosure can provide a piston for a compressor capable ofpreventing a heat loss and improving compression efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, that may be included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this specification, illustrate embodiments of the disclosure andtogether with the description serve to explain various principles of thedisclosure.

FIG. 1 is a perspective view of a compressor according to an embodimentof the disclosure.

FIG. 2 is a cross-sectional view illustrating a structure of acompressor according to an embodiment of the disclosure.

FIG. 3 is a perspective view of a piston for a compressor according toan embodiment of the disclosure.

FIG. 4 is an exploded perspective view of a piston for a compressoraccording to an embodiment of the disclosure.

FIG. 5 is a cross-sectional view of a partial configuration of FIG. 3.

FIG. 6 is a cross-sectional view of a piston for a compressor accordingto an embodiment of the disclosure.

FIGS. 7 and 8 are cross-sectional views of a piston for a compressoraccording to another embodiment of the disclosure.

FIGS. 9 and 10 are cross-sectional views of a piston for a compressoraccording to another embodiment of the disclosure.

FIG. 11 is a cross-sectional view of a piston for a compressor accordingto another embodiment of the disclosure.

FIG. 12 is a perspective view illustrating a piston for a compressoraccording to a related art.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the disclosure,examples of which are illustrated in the accompanying drawings. Whereverpossible, the same reference numbers will be used throughout thedrawings to refer to the same or like parts.

In embodiments of the disclosure, when an arbitrary component isdescribed as “being connected to” or “being coupled to” other component,it should be understood that another component(s) may exist betweenthem, although the arbitrary component may be directly connected orcoupled to the other component.

It will be noted that a detailed description of known arts will beomitted if it is determined that the detailed description of the knownarts can obscure embodiments of the disclosure. The accompanyingdrawings are used to help easily understand various technical featuresand it should be understood that embodiments presented herein are notlimited by the accompanying drawings. As such, the present disclosureshould be understand to extend to any alterations, equivalents andsubstitutes in addition to those which are particularly set out in theaccompanying drawings.

In addition, a term of “disclosure” may be replaced by document,specification, description, etc.

FIG. 1 is a perspective view of a compressor according to an embodimentof the disclosure.

Referring to FIG. 1, a linear compressor 100 according to an embodimentof the disclosure may include a shell 111 and shell covers 112 and 113coupled to the shell 111. In a broad sense, the shell covers 112 and 113can be understood as one configuration of the shell 111.

Legs 20 may be coupled to a lower side of the shell 111. The legs 20 maybe coupled to a base of a product on which the linear compressor 100 ismounted. For example, the product may include a refrigerator, and thebase may include a machine room base of the refrigerator. As anotherexample, the product may include an outdoor unit of an air conditioner,and the base may include a base of the outdoor unit.

The shell 111 may have a substantially cylindrical shape and may bedisposed to lie in a horizontal direction or an axial direction. FIG. 1illustrates that the shell 111 is extended in the horizontal directionand has a slightly low height in a radial direction, by way of example.That is, since the linear compressor 100 can have a low height, there isan advantage in that a height of the machine room can decrease when thelinear compressor 100 is installed in, for example, the machine roombase of the refrigerator.

A longitudinal central axis of the shell 111 coincides with a centralaxis of a main body of the compressor 100 to be described later, and thecentral axis of the main body of the compressor 100 coincides with acentral axis of a cylinder 140 and a piston 150 constituting the mainbody of the compressor 100.

A terminal 30 may be installed on an external surface of the shell 111.The terminal 30 may transmit external electric power to a drive unit 130of the linear compressor 100. More specifically, the terminal 30 may beconnected to a lead line of a coil 132 b.

A bracket 31 may be installed on the outside of the terminal 30. Thebracket 31 may include a plurality of brackets surrounding the terminal30. The bracket 31 may perform a function of protecting the terminal 30from an external impact, etc.

Both sides of the shell 111 may be opened. The shell covers 112 and 113may be coupled to both sides of the opened shell 111. More specifically,the shell covers 112 and 113 may include a first shell cover 112 coupledto one opened side of the shell 111 and a second shell cover 113 coupledto the other opened side of the shell 111. An inner space of the shell111 may be sealed by the shell covers 112 and 113.

FIG. 1 illustrates that the first shell cover 112 is positioned on theright side of the linear compressor 100, and the second shell cover 113is positioned on the left side of the linear compressor 100, by way ofexample. In other words, the first and second shell covers 112 and 113may be disposed to face each other. It can be understood that the firstshell cover 112 is positioned on a suction side of a refrigerant, andthe second shell cover 113 is positioned on a discharge side of therefrigerant.

The linear compressor 100 may include a plurality of pipes 114, 115, and40 that are included in the shell 111 or the shell covers 112 and 113and can suck, discharge, or inject the refrigerant.

The plurality of pipes 114, 115, and 40 may include a suction pipe 114that allows the refrigerant to be sucked into the linear compressor 100,a discharge pipe 115 that allows the compressed refrigerant to bedischarged from the linear compressor 100, and a supplementary pipe 40for supplementing the refrigerant in the linear compressor 100.

For example, the suction pipe 114 may be coupled to the first shellcover 112. The refrigerant may be sucked into the linear compressor 100along the axial direction through the suction pipe 114.

The discharge pipe 115 may be coupled to an outer circumferentialsurface of the shell 111. The refrigerant sucked through the suctionpipe 114 may be compressed while flowing in the axial direction. Thecompressed refrigerant may be discharged through the discharge pipe 115.The discharge pipe 115 may be disposed closer to the second shell cover113 than to the first shell cover 112.

The supplementary pipe 40 may be coupled to the outer circumferentialsurface of the shell 111. A worker may inject the refrigerant into thelinear compressor 100 through the supplementary pipe 40.

The supplementary pipe 40 may be coupled to the shell 111 at a differentheight from the discharge pipe 115 in order to prevent interference withthe discharge pipe 115. Here, the height may be understood as a distancemeasured from the leg 20 in a vertical direction. Because the dischargepipe 115 and the supplementary pipe 40 are coupled to the outercircumferential surface of the shell 111 at different heights, the workconvenience can be attained.

On an inner circumferential surface of the shell 111 corresponding to alocation at which the supplementary pipe 40 is coupled, at least aportion of the second shell cover 113 may be positioned adjacently. Inother words, at least a portion of the second shell cover 113 may act asa resistance of the refrigerant injected through the supplementary pipe40.

Thus, with respect to a flow path of the refrigerant, a size of the flowpath of the refrigerant introduced through the supplementary pipe 40 isconfigured to decrease by the second shell cover 113 while therefrigerant enters into the inner space of the shell 111, and againincrease while the refrigerant passes through the second shell cover113. In this process, a pressure of the refrigerant may be reduced tovaporize the refrigerant, and an oil contained in the refrigerant may beseparated. Thus, while the refrigerant, from which the oil is separated,is introduced into the piston 150, a compression performance of therefrigerant can be improved. The oil may be understood as a working oilpresent in a cooling system.

FIG. 2 is a cross-sectional view illustrating a structure of thecompressor 100.

Hereinafter, a compressor according to the present disclosure will bedescribed taking, as an example, a linear compressor that sucks andcompresses a fluid while a piston linearly reciprocates, and dischargesthe compressed fluid.

The linear compressor may be a component of a refrigeration cycle, andthe fluid compressed in the linear compressor may be a refrigerantcirculating the refrigeration cycle. The refrigeration cycle may includea condenser, an expander, an evaporator, etc., in addition to thecompressor. The linear compressor may be used as a component of thecooling system of the refrigerator, but is not limited thereto. Thelinear compressor can be widely used in the whole industry.

Referring to FIG. 2, the compressor 100 may include a casing 110 and amain body received in the casing 110. The main body of the compressor100 may include a frame 120, the cylinder 140 fixed to the frame 120,the piston 150 that linearly reciprocates inside the cylinder 140, thedrive unit 130 that is fixed to the frame 120 and gives a driving forceto the piston 150, and the like. Here, the cylinder 140 and the piston150 may be referred to as compression units 140 and 150.

The compressor 100 may include a bearing means for reducing a frictionbetween the cylinder 140 and the piston 150. The bearing means may be anoil bearing or a gas bearing. Alternatively, a mechanical bearing may beused as the bearing means.

The main body of the compressor 100 may be elastically supported bysupport springs 116 and 117 installed at both ends inside the casing110. The support springs 116 and 117 may include a first support spring116 for supporting the rear of the main body and a second support spring117 for supporting a front of the main body. The support springs 116 and117 may include a leaf spring. The support springs 116 and 117 canabsorb vibrations and impacts generated by a reciprocating motion of thepiston 150 while supporting the internal parts of the main body of thecompressor 100.

The casing 110 may form a sealed space. The sealed space may include areceiving space 101 in which the sucked refrigerant is received, asuction space 102 which is filled with the refrigerant before thecompression, a compression space 103 in which the refrigerant iscompressed, and a discharge space 104 which is filled with thecompressed refrigerant.

The refrigerant sucked from the suction pipe 114 connected to the rearside of the casing 110 may be filled in the receiving space 101, and therefrigerant in the suction space 102 communicating with the receivingspace 101 may be compressed in the compression space 103, dischargedinto the discharge space 104, and discharged to the outside through thedischarge pipe 115 connected to the front side of the casing 110.

The casing 110 may include the shell 111 formed in a substantiallycylindrical shape that is open at both ends and is long in a transversedirection, the first shell cover 112 coupled to the rear side of theshell 111, and the second shell cover 113 coupled to the front side ofthe shell 111. Here, it can be understood that the front side is theleft side of the figure and is a direction in which the compressedrefrigerant is discharged, and the rear side is the right side of thefigure and is a direction in which the refrigerant is introduced.Further, the first shell cover 112 and the second shell cover 113 may beformed as one body with the shell 11.

The casing 110 may be formed of a thermally conductive material. Hence,heat generated in the inner space of the casing 110 can be quicklydissipated to the outside.

The first shell cover 112 may be coupled to the shell 111 in order toseal the rear of the shell 111, and the suction pipe 114 may be insertedand coupled to the center of the first shell cover 112.

The rear of the main body of the compressor 100 may be elasticallysupported by the first support spring 116 in the radial direction of thefirst shell cover 112.

The first support spring 116 may include a circular leaf spring. An edgeof the first support spring 116 may be elastically supported by asupport bracket 123 a in a forward direction with respect to a backcover 123. An opened center portion of the first support spring 116 maybe supported by a suction guide 116 a in a rearward direction withrespect to the first shell cover 112.

The suction guide 116 a may have a through passage formed therein. Thesuction guide 116 a may be formed in a cylindrical shape. A front outercircumferential surface of the suction guide 116 a may be coupled to acentral opening of the first support spring 116, and a rear end of thesuction guide 116 a may be supported by the first shell cover 112. Inthis instance, a separate suction side support member 116 b may beinterposed between the suction guide 116 a and an inner surface of thefirst shell cover 112.

A rear side of the suction guide 116 a may communicate with the suctionpipe 114, and the refrigerant sucked through the suction pipe 114 maypass through the suction guide 116 a and may be smoothly introduced intoa muffler unit 160 to be described later.

A damping member 116 c may be disposed between the suction guide 116 aand the suction side support member 116 b. The damping member 116 c maybe formed of a rubber material or the like. Hence, a vibration that mayoccur in the process of sucking the refrigerant through the suction pipe114 can be prevented from being transmitted to the first shell cover112.

The second shell cover 113 may be coupled to the shell 111 to seal thefront side of the shell 111, and the discharge pipe 115 may be insertedand coupled through a loop pipe 115 a. The refrigerant discharged fromthe compression space 103 may pass through a discharge cover assembly180 and then may be discharged into the refrigeration cycle through theloop pipe 115 a and the discharge pipe 115.

A front side of the main body of the compressor 100 may be elasticallysupported by the second support spring 117 in the radial direction ofthe shell 111 or the second shell cover 113.

The second support spring 117 may include a circular leaf spring. Anopened center portion of the second support spring 117 may be supportedby a first support guide 117 b in a rearward direction with respect tothe discharge cover assembly 180. An edge of the second support spring117 may be supported by a support bracket 117 a in a forward directionwith respect to the inner surface of the shell 111 or the innercircumferential surface of the shell 111 adjacent to the second shellcover 113.

Unlike FIG. 2, the edge of the second support spring 117 may besupported in the forward direction with respect to the inner surface ofthe shell 111 or the inner circumferential surface of the shell 111adjacent to the second shell cover 113 through a separate bracket (notshown) coupled to the second shell cover 113.

The first support guide 117 b may be formed in a cylindrical shape. Across section of the first support guide 117 may have a plurality ofdiameters. A front side of the first support guide 117 may be insertedinto a central opening of the second support spring 117, and a rear sideof the first support guide 117 may be inserted into a central opening ofthe discharge cover assembly 180. A support cover 117 c may be coupledto the front side of the first support guide 117 b with the secondsupport spring 117 interposed therebetween. A cup-shaped second supportguide 117 d that is recessed forward may be coupled to the front side ofthe support cover 117 c. A cup-shaped third support guide 117 e thatcorresponds to the second support guide 117 d and is recessed rearwardmay be coupled to the inside of the second shell cover 113. The secondsupport guide 117 d may be inserted into the third support guide 117 eand may be supported in the axial direction and/or the radial direction.In this instance, a gap may be formed between the second support guide117 d and the third support guide 117 e.

The frame 120 may include a body portion 121 supporting the outercircumferential surface of the cylinder 140, and a first flange portion122 that is connected to one side of the body portion 121 and supportsthe drive unit 130. The frame 120 may be elastically supported withrespect to the casing 110 by the first and second support springs 116and 117 together with the drive unit 130 and the cylinder 140.

The body portion 121 may wrap the outer circumferential surface of thecylinder 140. The body portion 121 may be formed in a cylindrical shape.The first flange portion 122 may extend from a front end of the bodyportion 121 in the radial direction.

The cylinder 140 may be coupled to an inner circumferential surface ofthe body portion 121. An inner stator 134 may be coupled to an outercircumferential surface of the body portion 121. For example, thecylinder 140 may be pressed and fitted to the inner circumferentialsurface of the body portion 121, and the inner stator 134 may be fixedusing a separate fixing ring (not shown).

An outer stator 131 may be coupled to a rear surface of the first flangeportion 122, and the discharge cover assembly 180 may be coupled to afront surface of the first flange portion 122. For example, the outerstator 131 and the discharge cover assembly 180 may be fixed through amechanical coupling means.

On one side of the front surface of the first flange portion 122, abearing inlet groove 125 a forming a part of the gas bearing may beformed, a bearing communication hole 125 b penetrating from the bearinginlet groove 125 a to the inner circumferential surface of the bodyportion 121 may be formed, and a gas groove 125 c communicating with thebearing communication hole 125 b may be formed on the innercircumferential surface of the body portion 121.

The bearing inlet groove 125 a may be recessed to a predetermined depthin the axial direction. The bearing communication hole 125 b is a holehaving a smaller cross-sectional area than the bearing inlet groove 125a and may be inclined toward the inner circumferential surface of thebody portion 121. The gas groove 125 c may be formed in an annular shapehaving a predetermined depth and an axial length on the innercircumferential surface of the body portion 121. Alternatively, the gasgroove 125 c may be formed on the outer circumferential surface of thecylinder 140 in contact with the inner circumferential surface of thebody portion 121, or formed on both the inner circumferential surface ofthe body portion 121 and the outer circumferential surface of thecylinder 140.

In addition, a gas inlet 142 corresponding to the gas groove 125 c maybe formed on the outer circumferential surface of the cylinder 140. Thegas inlet 142 forms a kind of nozzle in the gas bearing.

The frame 120 and the cylinder 140 may be formed of aluminum or analuminum alloy material.

The cylinder 140 may be formed in a cylindrical shape that is open atboth ends. The piston 150 may be inserted through a rear end of thecylinder 140. A front end of the cylinder 140 may be closed via adischarge valve assembly 170. The compression space 103 may be formedbetween the cylinder 140, a front end of the piston 150, and thedischarge valve assembly 170. Here, the front end of the piston 150 maybe referred to as a head portion 151. The compression space 103increases in volume when the piston 150 moves backward, and decreases involume as the piston 150 moves forward. That is, the refrigerantintroduced into the compression space 103 may be compressed while thepiston 150 moves forward, and may be discharged through the dischargevalve assembly 170.

The cylinder 140 may include a second flange portion 141 disposed at thefront end. The second flange portion 141 may bend to the outside of thecylinder 140. The second flange portion 141 may extend in an outercircumferential direction of the cylinder 140. The second flange portion141 of the cylinder 140 may be coupled to the frame 120. For example,the front end of the frame 120 may include a flange groove correspondingto the second flange portion 141 of the cylinder 140, and the secondflange portion 141 of the cylinder 140 may be inserted into the flangegroove and coupled through a coupling member.

A gas bearing means may be provided to supply a discharge gas to a gapbetween the outer circumferential surface of the piston 150 and theouter circumferential surface of the cylinder 140 and lubricate betweenthe cylinder 140 and the piston 150 with gas. The discharge gas betweenthe cylinder 140 and the piston 150 may provide a floating force to thepiston 150 to reduce a friction generated between the piston 150 and thecylinder 140.

For example, the cylinder 140 may include the gas inlet 142. The gasinlet 142 may communicate with the gas groove 125 c formed on the innercircumferential surface of the body portion 121. The gas inlet 142 maypass through the cylinder 140 in the radial direction. The gas inlet 142may guide the compressed refrigerant introduced in the gas groove 125 cbetween the inner circumferential surface of the cylinder 140 and theouter circumferential surface of the piston 150. Alternatively, the gasgroove 125 c may be formed on the outer circumferential surface of thecylinder 140 in consideration of the convenience of processing.

An entrance of the gas inlet 142 may be formed relatively widely, and anexit of the gas inlet 142 may be formed as a fine through hole to serveas a nozzle. The entrance of the gas inlet 142 may further include afilter (not shown) blocking the inflow of foreign matter. The filter maybe a metal mesh filter, or may be formed by winding a member such asfine thread.

The plurality of gas inlets 142 may be independently formed.Alternatively, the entrance of the gas inlet 142 may be formed as anannular groove, and a plurality of exits may be formed along the annulargroove at regular intervals. The gas inlet 142 may be formed only at thefront side based on the axial middle of the cylinder 140. On thecontrary, the gas inlet 142 may be formed at the rear side based on theaxial middle of the cylinder 140 in consideration of the sagging of thepiston 150.

The piston 150 is inserted into the opened rear end of the cylinder 140and is provided to seal the rear of the compression space 103.

The piston 150 may include a head portion 151 and a guide portion 152.The head portion 151 may be formed in a disc shape. The head portion 151may be partially open. The head portion 151 may partition thecompression space 103. The guide portion 152 may extend rearward from anouter circumferential surface of the head portion 151. The guide portion152 may be formed in a cylindrical shape. The inside of the guideportion 152 may be empty, and a front of the guide portion 152 may bepartially sealed by the head portion 151. A rear of the guide portion152 may be opened and connected to the muffler unit 160. The headportion 151 may be provided as a separate member coupled to the guideportion 152. Alternatively, the head portion 151 and the guide portion152 may be formed as one body.

The piston 150 may include a suction port 154. The suction port 154 maypass through the head portion 151. The suction port 154 may communicatewith the suction space 102 and the compression space 103 inside thepiston 150. For example, the refrigerant flowing from the receivingspace 101 to the suction space 102 inside the piston 150 may passthrough the suction port 154 and may be sucked into the compressionspace 103 between the piston 150 and the cylinder 140.

The suction port 154 may extend in the axial direction of the piston150. The suction port 154 may be inclined in the axial direction of thepiston 150. For example, the suction port 154 may extend to be inclinedin a direction away from the central axis as it goes to the rear of thepiston 150.

A cross section of the suction port 154 may be formed in a circularshape. The suction port 154 may have a constant inner diameter. Incontrast, the suction port 154 may be formed as a long hole in which anopening extends in the radial direction of the head portion 151, or maybe formed such that the inner diameter becomes larger as it goes to therear.

The plurality of suction ports 154 may be formed in one or more of theradial direction and the circumferential direction of the head portion151.

The head portion 151 of the piston 150 adjacent to the compression space103 may be equipped with a suction valve 155 for selectively opening andclosing the suction port 154. The suction valve 155 may operate byelastic deformation to open or close the suction port 154. That is, thesuction valve 155 may be elastically deformed to open the suction port154 by the pressure of the refrigerant flowing into the compressionspace 103 through the suction port 154.

The piston 150 may be connected to a mover 135. The mover 135 mayreciprocate forward and backward according to the movement of the piston150. The inner stator 134 and the cylinder 140 may be disposed betweenthe mover 135 and the piston 150. The mover 135 and the piston 150 maybe connected to each other by a magnet frame 136 that is formed bydetouring the cylinder 140 and the inner stator 134 to the rear.

The muffler unit 160 may be coupled to the rear of the piston 150 toreduce a noise generated in the process of sucking the refrigerant intothe piston 150. The refrigerant sucked through the suction pipe 114 mayflow into the suction space 102 inside the piston 150 via the mufflerunit 160.

The muffler unit 160 may include a suction muffler 161 communicatingwith the receiving space 101 of the casing 110, and an inner guide 162that is connected to a front of the suction muffler 161 and guides therefrigerant to the suction port 154.

The suction muffler 161 may be positioned in the rear of the piston 150.A rear opening of the suction muffler 161 may be disposed adjacent tothe suction pipe 114, and a front end of the suction muffler 161 may becoupled to the rear of the piston 150. The suction muffler 161 may havea flow path formed in the axial direction to guide the refrigerant inthe receiving space 101 to the suction space 102 inside the piston 150.

The inside of the suction muffler 161 may include a plurality of noisespaces partitioned by a baffle. The suction muffler 161 may be formed bycombining two or more members. For example, a second suction muffler maybe press-coupled to the inside of a first suction muffler to form aplurality of noise spaces. In addition, the suction muffler 161 may beformed of a plastic material in consideration of weight or insulationproperty.

One side of the inner guide 162 may communicate with the noise space ofthe suction muffler 161, and other side may be deeply inserted into thepiston 150. The inner guide 162 may be formed in a pipe shape. Both endsof the inner guide 162 may have the same inner diameter. The inner guide162 may be formed in a cylindrical shape. Alternatively, an innerdiameter of a front end that is a discharge side of the inner guide 162may be greater than an inner diameter of a rear end opposite the frontend.

The suction muffler 161 and the inner guide 162 may be provided invarious shapes and may adjust the pressure of the refrigerant passingthrough the muffler unit 160. The suction muffler 161 and the innerguide 162 may be formed as one body.

The discharge valve assembly 170 may include a discharge valve 171 and avalve spring 172 that is provided on a front side of the discharge valve171 to elastically support the discharge valve 171. The discharge valveassembly 170 may selectively discharge the compressed refrigerant in thecompression space 103. Here, the compression space 103 means a spacebetween the suction valve 155 and the discharge valve 171.

The discharge valve 171 may be disposed to be supportable on the frontsurface of the cylinder 140. The discharge valve 171 may selectivelyopen and close the front opening of the cylinder 140. The dischargevalve 171 may operate by elastic deformation to open or close thecompression space 103. The discharge valve 171 may be elasticallydeformed to open the compression space 103 by the pressure of therefrigerant flowing into the discharge space 104 through the compressionspace 103. For example, the compression space 103 may maintain a sealedstate while the discharge valve 171 is supported on the front surface ofthe cylinder 140, and the compressed refrigerant of the compressionspace 103 may be discharged into an opened space in a state where thedischarge valve 171 is spaced apart from the front surface of thecylinder 140.

The valve spring 172 may be provided between the discharge valve 171 andthe discharge cover assembly 180 to provide an elastic force in theaxial direction. The valve spring 172 may be provided as a compressioncoil spring, or may be provided as a leaf spring in consideration of anoccupied space or reliability.

When the pressure of the compression space 103 is equal to or greaterthan a discharge pressure, the valve spring 172 may open the dischargevalve 171 while deforming forward, and the refrigerant may be dischargedfrom the compression space 103 and discharged into a first dischargespace 104 a of the discharge cover assembly 180. When the discharge ofthe refrigerant is completed, the valve spring 172 provides a restoringforce to the discharge valve 171 and thus can allow the discharge valve171 to be closed.

A process of introducing the refrigerant into the compression space 103through the suction valve 155 and discharging the refrigerant of thecompression space 103 to the discharge space 104 through the dischargevalve 171 is described as follows.

In the process in which the piston 150 linearly reciprocates inside thecylinder 140, if the pressure of the compression space 103 is equal toor less than a predetermined suction pressure, the suction valve 155 isopened and thus the refrigerant is sucked into a compression space 103.On the other hand, if the pressure of the compression space 103 exceedsthe predetermined suction pressure, the refrigerant of the compressionspace 103 is compressed in a state in which the suction valve 155 isclosed.

If the pressure of the compression space 103 is equal to or greater thanthe predetermined suction pressure, the valve spring 172 deforms forwardand opens the discharge valve 171 connected to the valve spring 172, andthe refrigerant is discharged from the compression space 103 to thedischarge space 104 of the discharge cover assembly 180. When thedischarge of the refrigerant is completed, the valve spring 172 providesa restoring force to the discharge valve 171 and allows the dischargevalve 171 to be closed, thereby sealing a front of the compression space103.

The discharge cover assembly 180 is installed at the front of thecompression space 103, forms a discharge space 104 for receiving therefrigerant discharged from the compression space 103, and is coupled toa front of the frame 120 to thereby reduce a noise generated in theprocess of discharging the refrigerant from the compression space 103.The discharge cover assembly 180 may be coupled to a front of the firstflange portion 122 of the frame 120 while receiving the discharge valveassembly 170. For example, the discharge cover assembly 180 may becoupled to the first flange portion 122 through a mechanical couplingmember.

An O-ring 166 may be provided between the discharge cover assembly 180and the frame 120 to prevent the refrigerant in a gasket 165 for thermalinsulation and the discharge space 104 from leaking.

The discharge cover assembly 180 may be formed of a thermally conductivematerial. Therefore, when a high temperature refrigerant is introducedinto the discharge cover assembly 180, heat of the refrigerant may betransferred to the casing 110 through the discharge cover assembly 180and dissipated to the outside of the compressor.

The discharge cover assembly 180 may include one discharge cover, or maybe arranged so that a plurality of discharge covers sequentiallycommunicates with each other. When the discharge cover assembly 180 isprovided with the plurality of discharge covers, the discharge space 104may include a plurality of spaces partitioned by the respectivedischarge covers. The plurality of spaces may be disposed in afront-rear direction and may communicate with each other.

For example, when there are three discharge covers, the discharge space104 may include a first discharge space 104 a between the frame 120 anda first discharge cover 181 coupled to the front side of the frame 120,a second discharge space 104 b between the first discharge cover 181 anda second discharge cover 182 that communicates with the first dischargespace 104 a and is coupled to a front side of the first discharge cover181, and a third discharge space 104 c between the second dischargecover 182 and a third discharge cover 183 that communicates with thesecond discharge space 104 b and is coupled to a front side of thesecond discharge cover 182.

The first discharge space 104 a may selectively communicate with thecompression space 103 by the discharge valve 171, the second dischargespace 104 b may communicate with the first discharge space 104 a, andthe third discharge space 104 c may communicate with the seconddischarge space 104 b. Hence, as the refrigerant discharged from thecompression space 103 sequentially passes through the first dischargespace 104 a, the second discharge space 104 b, and the third dischargespace 104 c, a discharge noise can be reduced, and the refrigerant canbe discharged to the outside of the casing 110 through the loop pipe 115a and the discharge pipe 115 communicating with the third dischargecover 183.

The drive unit 130 may include the outer stator 131 that is disposedbetween the shell 111 and the frame 120 and surrounds the body portion121 of the frame 120, the inner stator 134 that is disposed between theouter stator 131 and the cylinder 140 and surrounds the cylinder 140,and the mover 135 disposed between the outer stator 131 and the innerstator 134.

The outer stator 131 may be coupled to the rear of the first flangeportion 122 of the frame 120, and the inner stator 134 may be coupled tothe outer circumferential surface of the body portion 121 of the frame120. The inner stator 134 may be spaced apart from the inside of theouter stator 131, and the mover 135 may be disposed in a space betweenthe outer stator 131 and the inner stator 134.

The outer stator 131 may be equipped with a winding coil, and the mover135 may include a permanent magnet. The permanent magnet may consist ofa single magnet with one pole or configured by combining a plurality ofmagnets with three poles.

The outer stator 131 may include a coil winding 132 surrounding theaxial direction in the circumferential direction and a stator core 133stacked while surrounding the coil winding 132. The coil winding 132 mayinclude a hollow cylindrical bobbin 132 a and a coil 132 b wound in acircumferential direction of the bobbin 132 a. A cross section of thecoil 132 b may be formed in a circular or polygonal shape, for example,may have a hexagonal shape. In the stator core 133, a plurality oflamination sheets may be laminated radially, or a plurality oflamination blocks may be laminated along the circumferential direction.

The front side of the outer stator 131 may be supported by the firstflange portion 122 of the frame 120, and the rear side thereof may besupported by a stator cover 137. For example, the stator cover 137 maybe provided in a hollow disc shape, a front surface of the stator cover137 may be supported by the outer stator 131, and a rear surface thereofmay be supported by a resonant spring 118.

The inner stator 134 may be configured by stacking a plurality oflaminations on the outer circumferential surface of the body portion 121of the frame 120 in the circumferential direction.

One side of the mover 135 may be coupled to and supported by the magnetframe 136. The magnet frame 136 has a substantially cylindrical shapeand may be disposed to be inserted into a space between the outer stator131 and the inner stator 134. The magnet frame 136 may be coupled to therear side of the piston 150 to move together with the piston 150.

As an example, a rear end of the magnet frame 136 is bent and extendedinward in the radial direction to form a first coupling portion 136 a,and the first coupling portion 136 a may be coupled to a third flangeportion 153 formed in the rear of the piston 150. The first couplingportion 136 a of the magnet frame 136 and the third flange portion 153of the piston 150 may be coupled through a mechanical coupling member.

A fourth flange portion 161 a in front of the suction muffler 161 may beinterposed between the third flange portion 153 of the piston 150 andthe first coupling portion 136 a of the magnet frame 136. Thus, thepiston 150, the muffler unit 160, and the mover 135 can linearlyreciprocate together in a combined state.

When a current is applied to the drive unit 130, a magnetic flux may beformed in the winding coil, and an electromagnetic force may occur by aninteraction between the magnetic flux formed in the winding coil of theouter stator 131 and a magnetic flux formed by the permanent magnet ofthe mover 135 to move the mover 135. At the same time as the axialreciprocating movement of the mover 135, the piston 150 connected to themagnet frame 136 may also reciprocate integrally with the mover 135 inthe axial direction.

The drive unit 130 and the compression units 140 and 150 may besupported by the support springs 116 and 117 and the resonant spring 118in the axial direction.

The resonant spring 118 amplifies the vibration implemented by thereciprocating motion of the mover 135 and the piston 150 and thus canachieve an effective compression of the refrigerant. More specifically,the resonant spring 118 may be adjusted to a frequency corresponding toa natural frequency of the piston 150 to allow the piston 150 to performa resonant motion. Further, the resonant spring 118 generates a stablemovement of the piston 150 and thus can reduce the generation ofvibration and noise.

The resonant spring 118 may be a coil spring extending in the axialdirection. Both ends of the resonant spring 118 may be connected to avibrating body and a fixed body, respectively. For example, one end ofthe resonant spring 118 may be connected to the magnet frame 136, andthe other end may be connected to the back cover 123. Therefore, theresonant spring 118 may be elastically deformed between the vibratingbody vibrating at one end and the fixed body fixed to the other end.

A natural frequency of the resonant spring 118 may be designed to matcha resonant frequency of the mover 135 and the piston 150 during theoperation of the compressor 100, thereby amplifying the reciprocatingmotion of the piston 150. However, because the back cover 123 providedas the fixing body is elastically supported by the first support spring116 in the casing 110, the back cover 123 may not be strictly fixed.

The resonant spring 118 may include a first resonant spring 118 asupported on the rear side and a second resonant spring 118 b supportedon the front side based on a spring supporter 119.

The spring supporter 119 may include a body portion 119 a surroundingthe suction muffler 161, a second coupling portion 119 b that is bentfrom a front of the body portion 119 a in the inward radial direction,and a support portion 119 c that is bent from the rear of the bodyportion 119 a in the outward radial direction.

A front surface of the second coupling portion 119 b of the springsupporter 119 may be supported by the first coupling portion 136 a ofthe magnet frame 136. An inner diameter of the second coupling portion119 b of the spring supporter 119 may cover an outer diameter of thesuction muffler 161. For example, the second coupling portion 119 b ofthe spring supporter 119, the first coupling portion 136 a of the magnetframe 136, and the third flange portion 153 of the piston 150 may besequentially disposed and then integrally coupled via a mechanicalmember. In this instance, the description that the fourth flange portion161 a of the suction muffler 161 can be interposed between the thirdflange portion 153 of the piston 150 and the first coupling portion 136a of the magnet frame 136, and they can be fixed together is the same asthat described above.

The first resonant spring 118 a may be disposed between a front surfaceof the back cover 123 and a rear surface of the spring supporter 119.The second resonant spring 118 b may be disposed between a rear surfaceof the stator cover 137 and a front surface of the spring supporter 119.

A plurality of first and second resonant springs 118 a and 118 b may bedisposed in the circumferential direction of the central axis. The firstresonant springs 118 a and the second resonant springs 118 b may bedisposed parallel to each other in the axial direction, or may bealternately disposed. The first and second resonant springs 118 a and118 b may be disposed at regular intervals in the radial direction ofthe central axis. For example, three first resonant springs 118 a andthree second resonant springs 118 b may be provided and may be disposedat intervals of 120 degrees in the radial direction of the central axis.

The compressor 100 may include a plurality of sealing members that canincrease a coupling force between the frame 120 and the componentsaround the frame 120.

For example, the plurality of sealing members may include a firstsealing member that is interposed at a portion where the frame 120 andthe discharge cover assembly 180 are coupled and is inserted into aninstallation groove provided at the front end of the frame 120, and asecond sealing member that is provided at a portion at which the frame120 and the cylinder 140 are coupled and is inserted into aninstallation groove provided at an outer surface of the cylinder 140.The second sealing member can prevent the refrigerant of the gas groove125 c between the inner circumferential surface of the frame 120 and theouter circumferential surface of the cylinder 140 from leaking to theoutside, and can increase a coupling force between the frame 120 and thecylinder 140. The plurality of sealing members may further include athird sealing member that is provided at a portion at which the frame120 and the inner stator 134 are coupled and is inserted into aninstallation groove provided at the outer surface of the frame 120.Here, the first to third sealing members may have a ring shape.

An operation of the linear compressor 100 described above is as follows.

First, when a current is applied to the drive unit 130, a magnetic fluxmay be formed in the outer stator 131 by the current flowing in the coil132 b. The magnetic flux formed in the outer stator 131 may generate anelectromagnetic force, and the mover 135 including the permanent magnetmay linearly reciprocate by the generated electromagnetic force. Theelectromagnetic force is generated in a direction (forward direction) inwhich the piston 150 is directed toward a top dead center (TDC) during acompression stroke, and is alternately generated in a direction(rearward direction) in which the piston 150 is directed toward a bottomdead center (BDC) during a suction stroke. That is, the drive unit 130may generate a thrust which is a force for pushing the mover 135 and thepiston 150 in a moving direction.

The piston 150 linearly reciprocating inside the cylinder 140 mayrepeatedly increase or reduce volume of the compression space 103.

When the piston 150 moves in a direction (rearward direction) ofincreasing the volume of the compression space 103, a pressure of thecompression space 103 may decrease. Hence, the suction valve 155 mountedin front of the piston 150 is opened, and the refrigerant remaining inthe suction space 102 may be sucked into the compression space 103 alongthe suction port 154. The suction stroke may be performed until thepiston 150 is positioned in the bottom dead center by maximallyincreasing the volume of the compression space 103.

The piston 150 reaching the bottom dead center may perform thecompression stroke which switching its motion direction and moving in adirection (forward direction) of reducing the volume of the compressionspace 103. As the pressure of the compression space 103 increases duringthe compression stroke, the sucked refrigerant may be compressed. Whenthe pressure of the compression space 103 reaches a setting pressure,the discharge valve 171 is pushed out by the pressure of the compressionspace 103 and is opened from the cylinder 140, and the refrigerant canbe discharged into the discharge space 104 through a separation space.The compression stroke can continue while the piston 150 moves to thetop dead center at which the volume of the compression space 103 isminimized.

As the suction stroke and the compression stroke of the piston 150 arerepeated, the refrigerant introduced into the receiving space 101 insidethe compressor 100 through the suction pipe 114 may be introduced intothe suction space 102 inside the piston 150 by sequentially passing thesuction guide 116 a, the suction muffler 161, and the inner guide 162,and the refrigerant of the suction space 102 may be introduced into thecompression space 103 inside the cylinder 140 during the suction strokeof the piston 150. After the refrigerant of the compression space 103 iscompressed and discharged into the discharge space 104 during thecompression stroke of the piston 150, the refrigerant may be dischargedto the outside of the compressor 100 via the loop pipe 115 a and thedischarge pipe 115.

FIG. 3 is a perspective view of a piston for a compressor according toan embodiment of the disclosure. FIG. 4 is an exploded perspective viewof a piston for a compressor according to an embodiment of thedisclosure. FIG. 5 is a cross-sectional view of a partial configurationof FIG. 3. FIG. 6 is a cross-sectional view of a piston for a compressoraccording to an embodiment of the disclosure.

Referring to FIGS. 3 to 6, a piston 200 according to an embodiment ofthe disclosure may include a sliding portion 210, a head portion 220, aheat insulating member 230, a suction valve 300, and a coupling member400, but can be implemented except some of these components and does notexclude additional components.

The piston 200 may be used in the compressor 100 that compresses anddischarges a refrigerant sucked into the cylinder 140. The piston 200may be disposed in the cylinder 140. The piston 200 may include asuction space 102 receiving the refrigerant sucked therein. Thecompression space 103 may be formed at a front of the piston 200. Thepiston 200 may be formed in a cylindrical shape.

The piston 200 may include the sliding portion 210. The sliding portion210 may be disposed in the cylinder 140. The sliding portion 210 mayinclude the suction space 102 receiving the refrigerant sucked therein.At a front of the sliding portion 210, the head portion 220, the heatinsulating member 230, the suction valve 300, and the coupling member400 may be disposed. The sliding portion 210 may be formed in acylindrical shape. The sliding portion 210 may extend in the axialdirection to correspond to an inner wall shape of the cylinder 140. Thesliding portion 210 may be hollow and have a predetermined thickness ina circumferential direction. The suction space 102 may be formed in thesliding portion 210.

An outer wall of the sliding portion 210 may face an inner wall of thecylinder 140. The sliding portion 210 may linearly reciprocate forwardand backward inside the cylinder 140. The outer wall of the slidingportion 210 may generate a friction with the inner wall of the cylinder140. To prevent this, a surface processing for reducing the friction maybe performed on an outer circumferential surface of the sliding portion210. The surface processing can improve a wear resistance, lubricity ora thermal resistance. In this instance, the surface processing may beperformed on an inner circumferential surface of the cylinder 140 aswell as the outer circumferential surface of the sliding portion 210.

The surface processing of the sliding portion 210 may be performed onboth its outer circumferential surface and inner circumferentialsurface. In this case, the surface processing may be simultaneouslyperformed on the outer circumferential surface and the innercircumferential surface of the sliding portion 210. When the surfaceprocessing is performed only on the outer circumferential surface of thesliding portion 210, there is an advantage in that a coating materialcan be saved. When the surface processing is performed on both the outercircumferential surface and the inner circumferential surface of thesliding portion 210, there is an advantage in that the surfaceprocessing is simplified.

The surface processing of the sliding portion 210 may use one of diamondlike carbon (DLC), polytetrafluoroethylene (PTFE) (Teflon), a nickel(Ni)-phosphorus (P) alloy material, and an anodizing layer.

DLC is an amorphous carbon-based new material and contains a material inthe form of a thin film formed by electrically accelerating carbon ionsor activated hydrocarbon molecules in the plasma and hitting them on thesurface.

Since the properties of DLC are similar to that of diamond and have highhardness, a wear resistance, excellent electrical insulation, and a lowfriction coefficient, DLC has excellent lubricity characteristics.

As another example, PTFE is sprayed onto a coated object in a state inwhich a fluorine resin is coated, and is heated and fired at apredetermined temperature to form an inert coating layer. Since PTFE hasa low friction coefficient, it can improve lubricity of the surface anda wear resistance.

As another example, the Ni—P alloy material may be included in the outercircumferential surface of the piston 200 or the inner circumferentialsurface of the cylinder 140 by an electroless nickel plating method, andmay be formed by surface-depositing a nickel component and a phosphoruscomponent with a uniform thickness. The Ni—P alloy material may have achemical composition ratio of 90 to 92% of nickel (Ni) and 9 to 10% ofphosphorus (P). The Ni—P alloy material improves a corrosion resistanceand a wear resistance of the surface and has excellent lubricitycharacteristics.

As another example, an anodizing technology is a kind of aluminumpainted coating and is a processing technology in which an aluminumsurface is oxidized by oxygen generated in an anode when aluminum isused as the anode and electric current flows therein, and an aluminumoxide layer is formed. The anodizing technology has characteristics ofexcellent corrosion resistance and excellent insulation resistance.

The piston 200 may include the head portion 220. The head portion 220may be coupled to the front of the sliding portion 210. A cross sectionof the head portion 220 may have a circular shape. The head portion 220may have a disc shape. The head portion 220 may selectively (orpartially) close a front opening of the sliding portion 210. Here, thepartially closing may mean to close a portion except a suction port 222.The head portion 220 may be provided as a separate member that isinserted and coupled to the front opening of the sliding portion 210. Onthe contrary, the head portion 220 may be formed integrally with thesliding portion 210.

The head portion 220 may be formed in a cylindrical shape extending inthe axial direction. An outer diameter of the head portion 220 may beprovided to correspond to an inner diameter of the sliding portion 210.The head portion 220 may be press-fitted to the sliding portion 210 ormay be coupled to the sliding portion 210 through an adhesive.Alternatively, the outer diameter of the head portion 220 may beprovided to correspond to an outer diameter of the sliding portion 210.In this case, the head portion 220 may be coupled to the front of thesliding portion 210 using an adhesive, etc.

A compression space 103 may be formed at a front of the head portion220. The suction space 102 may be formed at the rear of the head portion220.

The head portion 220 may include the suction port 222. The suction port222 may communicate the compression space 103 with the suction space102. The suction port 222 may be formed in a cylindrical shape. Thesuction port 222 may be formed on the front surface of the head portion220. The suction port 222 may be formed to protrude forward from thefront surface of the head portion 220. The suction port 222 may bedisposed in the heat insulating member 230. The suction port 222 may bedisposed in a suction port hole 232 of the heat insulating member 230.The suction port 222 may be spaced apart from a coupling port 224. Thesuction port 222 may be formed in a region between a central region andan edge region of the front surface of the head portion 220. The suctionport 222 may include a hole therein. The suction port 222 may include aplurality of suction ports. The plurality of suction ports may be spacedapart from each other. The plurality of suction ports may be disposed atpositions symmetrical to each other about the coupling port 224.

The head portion 220 may include the coupling port 224. The couplingport 224 may be formed in a cylindrical shape. The coupling port 224 maybe formed on the front surface of the head portion 220. The couplingport 224 may be formed to protrude forward from the front surface of thehead portion 220. The coupling port 224 may be disposed in the heatinsulating member 230. The coupling port 224 may be disposed in acoupling port hole 234 of the heat insulating member 230. The couplingport 224 may be spaced apart from the suction port 222. The couplingport 224 may be formed in the central region of the front surface of thehead portion 220. The coupling member 400 may be fastened to thecoupling port 224.

The piston 200 may include the heat insulating member 230. The heatinsulating member 230 may be disposed in front of the sliding portion210. The heat insulating member 230 may be disposed in front of the headportion 220. The heat insulating member 230 may be coupled to the headportion 220. The heat insulating member 230 may be coupled to the frontof the head portion 220. The heat insulating member 230 may be coupledto the front surface of the head portion 220. The heat insulating member230 may be formed in a disc shape or a cylindrical shape. The heatinsulating member 230 may be formed of a material with low thermalconductivity. Hence, the heat insulating member 230 can prevent heattransfer to the cylinder 140, pistons 150 and 200, and suckedrefrigerant of a relatively low temperature generated as a hightemperature and high pressure gas compressed in the compression space103 acts as a heat source.

The heat insulating member 230 may include the suction port hole 232.The suction port hole 232 may pass through the heat insulating member230. The suction port hole 232 may pass through the heat insulatingmember 230 along the axial direction. A cross section of the suctionport hole 232 may have a circular shape. The suction port 222 may bedisposed in the suction port hole 232. The suction port 222 may bedisposed in the suction port hole 232. The suction port hole 232 may bepenetrated by the suction port 222. An inner diameter of the suctionport hole 232 may correspond to an outer diameter of the suction port222. The suction port 222 may be fitted to the suction port hole 232.Hence, space efficiency can be improved. An axial length of the suctionport hole 232 may correspond to an axial length of the suction port 222.The suction port hole 232 may be formed in a region between a centralregion and an edge region of the heat insulating member 230. The suctionport hole 232 may be spaced apart from a coupling port hole 234. Thesuction port hole 232 may include a plurality of suction port holes. Theplurality of suction port holes 232 may be disposed at positionssymmetrical to each other based on the coupling port hole 234.

The heat insulating member 230 may include the coupling port hole 234.The coupling port hole 234 may pass through the heat insulating member230. The coupling port hole 234 may pass through the heat insulatingmember 230 along the axial direction. A cross section of the couplingport hole 234 may have a circular shape. The coupling port 224 may bedisposed in the coupling port hole 234. The coupling port hole 234 maybe penetrated by the coupling port 224. An inner diameter of thecoupling port hole 234 may correspond to an outer diameter of thecoupling port 224. The coupling port 224 may be fitted to the couplingport hole 234. Hence, space efficiency can be improved. An axial lengthof the coupling port hole 234 may correspond to an axial length of thecoupling port 224. The coupling port hole 234 may be formed in thecentral region of the heat insulating member 230. The coupling port hole234 may be spaced apart from the suction port hole 232.

The piston 200 may include the suction valve 300. The suction valve 300may be coupled to the front of the piston 200. The suction valve 300 maybe coupled to the front of the head portion 220. The suction valve 300may be coupled to a front of the heat insulating member 230. The suctionvalve 300 may be coupled to a front surface of the heat insulatingmember 230.

The suction valve 300 may be formed of a thin plate member or sheet witha circular shape. The suction valve 300 may be provided to reversiblymodify its shape. Hence, during a suction stroke in which the piston 200reverses, the suction valve 300 may be modified to open the suction port222 and allow the refrigerant of the suction space 102 to be dischargedinto the compression space 103. During a compression stroke in which thepiston 200 moves forward, the suction valve 300 may close the suctionport 222 and prevent the refrigerant from returning again to the suctionspace 102.

The suction valve 300 may open selectively the suction port 222. Morespecifically, the suction valve 300 may have a movement to repeatedlyclose or open the suction port 222 while going through the compressionstroke and the suction stroke.

The suction valve 300 may include a fixing portion, at the center, fixedto the front surface of the heat insulating member 230, a wing portion,in a peripheral region, that can be modified to close or open thesuction port 222, and a connection portion that connects the fixingportion to the wing portion.

An embodiment of the present disclosure is described by taking anexample where the suction valve 300 is the partial configuration of thepiston 200, but the suction valve 300 may also be understood as a memberseparate from the piston 200.

The piston 200 may include the coupling member 400. The coupling member400 may couple the heat insulating member 230 and the suction valve 300to the front of the head portion 220. The coupling member 400 may passthrough the fixing portion of the suction valve 300. The coupling member400 may pass through the coupling port hole 234 of the heat insulatingmember 230. The coupling member 400 may be coupled to the coupling port224. Hence, the coupling member 400 can couple the heat insulatingmember 230 of the suction valve 300 to the head portion 220.

An embodiment of the present disclosure is described by taking anexample where the coupling member 400 is the partial configuration ofthe piston 200, but the coupling member 400 may also be understood as amember separate from the piston 200. Further, an embodiment of thepresent disclosure is described by taking an example where the couplingmember 400 is screwed to the coupling port 224, but can be variouslychanged.

FIGS. 7 and 8 are cross-sectional views of a piston for a compressoraccording to another embodiment of the disclosure.

Referring to FIGS. 7 and 8, a piston 200 according to another embodimentof the disclosure may include a sliding portion 210, a head portion 220,a press-fit cap 240, a first elastic member 250, a second elastic member260, a suction valve 300, and a coupling member 400, but can beimplemented except some of these components and does not excludeadditional components.

Detailed configuration of the piston 200 according to another embodimentof the disclosure which is not described below can be understood tocorrespond to the detailed configuration of the piston 200 according toan embodiment of the disclosure.

The head portion 220 may include a suction port 226. A cross section ofthe suction port 226 may have a circular shape. The suction port 226 maypass through the head portion 220 along the axial direction. The suctionport 226 may be understood as a hole. The suction port 226 maycommunicate a compression space 103 with a suction space 102. Thesuction port 226 may be spaced apart from a coupling groove 228. Thesuction port 226 may be formed in a region between a central region andan edge region of the head portion 220. The suction port 226 may includea plurality of suction ports. The plurality of suction ports may bespaced apart from each other. The plurality of suction ports may bedisposed at positions symmetrical to each other about the couplinggroove 228.

The head portion 220 may include the coupling groove 228. The couplinggroove 228 may be formed to be recessed rearward from a front surface ofthe head portion 220. The coupling groove 228 may be formed in a centralregion of the front surface of the head portion 220. The coupling member400 may be fastened to the coupling groove 228.

The piston 200 may include the press-fit cap 240. The press-fit cap 240may be disposed in front of the sliding portion 210. The press-fit cap240 may be coupled to a front of the head portion 220. The press-fit cap240 may be formed in a cylindrical shape with an opened rear. Thepress-fit cap 240 may include an upper plate and a side plate extendingfrom the upper plate. The upper plate of the press-fit cap 240 may bespaced apart from the head portion 220. The first elastic member 250 maybe disposed in a separation space between the upper plate of thepress-fit cap 240 and the head portion 220. A rear surface of the sideplate of the press-fit cap 240 may be disposed on the front surface ofthe head portion 220.

The press-fit cap 240 may include a suction hole 242. The suction hole242 may communicate with the suction port 226. A cross section of thesuction hole 242 may have a circular shape. The suction hole 242 may beformed on the upper plate of the press-fit cap 240. The suction hole 242may be formed in a region between a central region and an edge region ofthe upper plate of the press-fit cap 240. The suction hole 242 may bespaced apart from a coupling hole 244. The suction hole 242 may includea plurality of suction holes. The plurality of suction holes may bedisposed at positions symmetrical to each other about the coupling hole244.

The press-fit cap 240 may include the coupling hole 244. The couplinghole 244 may communicate with the coupling groove 228. A cross sectionof the coupling hole 244 may have a circular shape. The coupling hole244 may be formed on the upper plate of the press-fit cap 240. Thecoupling hole 244 may be formed in the central region of the upper plateof the press-fit cap 240. The coupling hole 244 may be spaced apart fromthe suction hole 242.

The piston 200 may include the first elastic member 250. The firstelastic member 250 may be disposed between the press-fit cap 240 and thehead portion 220. The first elastic member 250 may be formed of amaterial with elasticity. The first elastic member 250 may be formed ina circular band shape. The first elastic member 250 may be referred toas an O-ring. The first elastic member 250 may be formed inside thesuction port 226. The first elastic member 250 may be disposed in aseparation space between the upper plate of the press-fit cap 240 andthe head portion 220. An axial length of the first elastic member 250may correspond to an axial length of the separation space between theupper plate of the press-fit cap 240 and the head portion 220. The firstelastic member 250 may be formed outside the coupling groove 228. Thefirst elastic member 250 may be disposed at a position corresponding toan area between the coupling groove 228 and the suction port 226. Thefirst elastic member 250 allows securing a space in which a gas layercan be formed therein.

The piston 200 may include the second elastic member 260. The secondelastic member 260 may be disposed between the press-fit cap 240 and thehead portion 220. The second elastic member 260 may be formed of amaterial with elasticity. The second elastic member 260 may be formed ina circular band shape. The second elastic member 260 may be referred toas an O-ring. The second elastic member 260 may be formed outside thesuction port 226. The second elastic member 260 may be formed outsidethe first elastic member 250. A space between the first elastic member250 and the second elastic member 260 may communicate with the suctionport 226 and the suction hole 242. The second elastic member 260 maycontact an inside surface of the upper plate of the press-fit cap 240,an inside surface of the side plate of the press-fit cap 240, and thefront surface of the head portion 220. The second elastic member 260 canprevent a gas passing through the suction port 226 and the suction hole242 from leaking.

The piston 200 may include the coupling member 400. The coupling member400 may couple the suction valve 300 and the press-fit cap 240 to thefront of the head portion 220. The coupling member 400 may pass throughthe coupling hole 244. The coupling member 400 may be fastened to thecoupling groove 228. When the coupling member 400 passes through thecoupling hole 244 and is fastened to the coupling groove 228, thecoupling member 400 can couple the suction valve 300 and the press-fitcap 240 to the head portion 220, and at the same time can seal betweenthe head portion 220, the press-fit cap 240, and the first elasticmember 250 from the outside. Hence, a gas layer 270 can be formedbetween the head portion 220, the press-fit cap 240, and the firstelastic member 250. Further, the gas layer 270 with low thermalconductivity can prevent heat transfer to the cylinder 140, pistons 150and 200, and sucked refrigerant of a relatively low temperaturegenerated as a high temperature and high pressure gas compressed in thecompression space 103 acts as a heat source. The gas layer 270 may be anair layer, but may be filled with other gases with low thermalconductivity.

FIGS. 9 and 10 are cross-sectional views of a piston for a compressoraccording to another embodiment of the disclosure.

Referring to FIGS. 9 and 10, a piston 200 according to anotherembodiment of the disclosure may include a sliding portion 210, a headportion 220, a press-fit cap 240, a first elastic member 250, a secondelastic member 260, a suction valve 300, and a coupling member 400, butcan be implemented except some of these components and does not excludeadditional components.

Detailed configuration of the piston 200 according to another embodimentof the disclosure which is not described below can be understood tocorrespond to the detailed configuration of the piston 200 according toan embodiment of the disclosure.

The head portion 220 may include a gas groove 229. The gas groove 229may be formed to be recessed rearward from a front surface of the headportion 220. The gas groove 229 may be disposed between a suction port226 and a coupling groove 228. The gas groove 229 may be formed in acircular band shape. Hence, a gas layer 270 can be formed between thehead portion 220, the press-fit cap 240, the first elastic member 250,and the gas groove 229. Since the gas layer 270 is formed in a widerarea than other embodiments of the present disclosure, this can improvethe efficiency of preventing heat transfer to the cylinder 140, pistons150 and 200, and sucked refrigerant of a relatively low temperaturegenerated as a high temperature and high pressure gas compressed in acompression space 103 acts as a heat source.

FIG. 11 is a cross-sectional view of a piston for a compressor accordingto another embodiment of the disclosure.

Referring to FIG. 11, a piston 200 according to another embodiment ofthe disclosure may include a sliding portion 210, a head portion 220, aheat insulating member 230, a first elastic member 250, a second elasticmember 260, a suction valve 300, and a coupling member 400, but can beimplemented except some of these components and does not excludeadditional components.

Detailed configuration of the piston 200 according to another embodimentof the disclosure which is not described below can be understood to bethe same as the detailed configuration of the piston 200 according to anembodiment of the disclosure.

The piston 200 may include the first elastic member 250. The firstelastic member 250 may be disposed between the heat insulating member230 and the head portion 220. The first elastic member 250 may be formedof a material with elasticity. The first elastic member 250 may beformed in a circular band shape. The first elastic member 250 may bereferred to as an O-ring. The first elastic member 250 may be formedinside a suction port 222. The first elastic member 250 may be disposedoutside a coupling port 224. The first elastic member 250 may bedisposed inside the second elastic member 260. The first elastic member250 allows securing a space in which a gas layer can be formed therein.

The piston 200 may include the second elastic member 260. The secondelastic member 260 may be disposed between the heat insulating member230 and the head portion 220. The second elastic member 260 may beformed of a material with elasticity. The second elastic member 260 maybe formed in a circular band shape. The second elastic member 260 may bereferred to as an O-ring. The second elastic member 260 may be disposedoutside the suction port 222. The second elastic member 260 may bedisposed outside the first elastic member 250. The suction port 222 maybe disposed in a space between the first elastic member 250 and thesecond elastic member 260. The second elastic member 260 may contact arear surface of the heat insulating member 230 and a front surface ofthe head portion 220.

A gas layer 270 can be formed in a space between the head portion 220,the heat insulating member 230 and the first elastic member 250. The gaslayer 270 with low thermal conductivity and the heat insulating member230 can prevent heat transfer to the cylinder 140, pistons 150 and 200,and sucked refrigerant of a relatively low temperature generated as ahigh temperature and high pressure gas compressed in a compression space103 acts as a heat source. The gas layer 270 may be an air layer, butmay be filled with other gases with low thermal conductivity.

As described herein, the heat transfer in the compressor 100 mainlyoccurs in the head portion 220 of the pistons 150 and 200. That is,because the heat insulating member 230 and the gas layer 270 accordingto embodiments of the disclosure are disposed in the head portion 220,the heat insulating member 230 and the gas layer 270 can prevent heattransfer to the cylinder 140, pistons 150 and 200, and suckedrefrigerant of a relatively low temperature generated as a hightemperature and high pressure gas compressed in the compression space103 acts as a heat source.

Some embodiments or other embodiments of the disclosure described aboveare not exclusive or distinct from each other. Some embodiments or otherembodiments of the disclosure described above can be used together orcombined in configuration or function.

For example, a configuration “A” described in an embodiment and/or thedrawings and a configuration “B” described in another embodiment and/orthe drawings can be combined with each other. That is, although thecombination between the configurations is not directly described, thecombination is possible except if it is described that the combinationis impossible.

The above detailed description is merely an example and is not to beconsidered as limiting the present disclosure. The scope of the presentdisclosure should be determined by rational interpretation of theappended claims, and all variations within the equivalent scope of thepresent disclosure are included in the scope of the present disclosure.

What is claimed is:
 1. A piston for a compressor, wherein the compressorincludes a cylinder configured to receive a refrigerant and isconfigured to compress and discharge the refrigerant in the cylinder,the piston comprising: a sliding portion that is disposed in thecylinder and that defines a suction space that receives the refrigerant;a head portion connected to the sliding portion and including a suctionport that fluidly communicates with a compression space and the suctionspace, wherein the compression space is defined at a first side of thehead portion, and wherein the suction space is defined at a second sideof the head portion opposite to the first side of the head portion; acap connected to the first side of the head portion, the cap including asuction hole that fluidly communicates with the suction port of the headportion; and a first elastic member disposed between the cap and thehead portion, wherein the head portion, the cap, and the first elasticmember define a gas layer, and wherein the gas layer is sealed by thehead portion, the cap, and the first elastic member.
 2. The piston forthe compressor of claim 1, wherein the first elastic member has acircular band shape.
 3. The piston for the compressor of claim 2,wherein the first elastic member is disposed radially closer to an axisof the piston than the suction port of the head portion.
 4. The pistonfor the compressor of claim 2, further comprising a second elasticmember disposed between the cap and the head portion around the firstelastic member.
 5. The piston for the compressor of claim 4, wherein thesecond elastic member has a circular band shape, and wherein the secondelastic member is disposed radially farther from an axis of the pistonthan the suction port of the head portion.
 6. The piston for thecompressor of claim 4, wherein a space between the first elastic memberand the second elastic member fluidly communicates with the suction portand the suction hole.
 7. The piston for the compressor of claim 1,wherein the head portion comprises a coupling groove that is defined atthe first side of the head portion and spaced apart from the suctionport.
 8. The piston for the compressor of claim 7, further comprising acoupling member that couples the cap to the first side of the headportion, wherein the cap comprises a coupling hole that is aligned withthe coupling groove of the head portion, and wherein the coupling memberextends through the coupling hole and is coupled to the coupling groove.9. The piston for the compressor of claim 7, wherein the first elasticmember is disposed between the coupling groove and the suction port. 10.The piston for the compressor of claim 7, wherein the head portioncomprises a gas groove between the coupling groove and the suction port.11. The piston for the compressor of claim 10, wherein the head portion,the cap, the first elastic member, and the gas groove define the gaslayer.
 12. The piston for the compressor of claim 10, wherein the gasgroove extends axially at the first side of the head portion.
 13. Thepiston for the compressor of claim 12, wherein the gas groove has acircular band shape.
 14. A piston for a compressor, wherein thecompressor includes a cylinder configured to receive a refrigerant andis configured to compress and discharge the refrigerant in the cylinder,the piston comprising: a sliding portion that is disposed in thecylinder and that defines a suction space that receives the refrigerant;a head portion connected to the sliding portion and including a suctionport that fluidly communicates with a compression space and the suctionspace, wherein the compression space is defined at a first side of thehead portion, and wherein the suction space is defined at a second sideof the head portion opposite to the first side of the head portion; anda heat insulating member connected to the first side of the headportion, the heat insulating member including a suction port receptionhole that at least partially receives the suction port of the headportion.
 15. The piston for the compressor of claim 14, wherein thesuction port protrudes axially from the first side of the head portion.16. The piston for the compressor of claim 15, wherein the head portioncomprises a coupling port that protrudes axially from the first side ofthe head portion and is spaced apart from the suction port.
 17. Thepiston for the compressor of claim 16, further comprising a couplingmember that couples the heat insulating member to the first side of thehead portion, wherein the heat insulating member comprises a couplingport reception hole that at least partially receives the coupling port,and wherein the coupling member extends through the coupling portreception hole and is coupled to the coupling port.
 18. The piston forthe compressor of claim 14, further comprising a first elastic memberdisposed between the heat insulating member and the head portion,wherein the head portion, the heat insulating member, and the firstelastic member define a gas layer.
 19. The piston for the compressor ofclaim 18, wherein the first elastic member has a circular band shape.20. The piston for the compressor of claim 18, further comprising asecond elastic member disposed between the heat insulating member andthe head portion around the first elastic member.